By Ajit Krishna Dasa
An interesting and persuasive argument for the existence of God is The Moral Argument. The argument can be presented as follows.
Premise 1: If God does not exist, absolute moral values do not exist.
Premise 2: Absolute moral values do exist.
Conclusion: Therefore God exists.
Defending premise one
Absolute moral values are values that exist objectively and are true for all human beings, even if only some or none of us agree on them, know about their existence, and even if it is possible for us to act contrary to them. Some people argue that the existence of God is not a necessary precondition for the existence of absolute moral values. They will hold that absolute moral values can exist independently of any personal being. This runs contrary to our experience which constantly affirms that all moral values are contingent upon personal beings. Based on our experience we have the following inductive argument:
Premise 1: All observed values are contingent upon personal beings.
Premise 2: A is a value.
Conclusion: Therefore A is contingent upon a personal being.
Moving on from here, it is obvious that fallible and limited human minds cannot establish absolute moral values. Since moral values are always contingent upon personal beings it seems likely that absolute values, if they exist, must be made by an absolute personal being with absolute power so that no other person can change or overrule this personal being’s established moral values. If someone could they would not be absolute.
Most atheists actually agree with this premise, and therefore they have to reject the second premise in order to avoid the conclusion.
Defending premise two
Either absolute moral values exist, or they do not exist. If they exist then moral absolutism is true, and if they do not exist then moral relativism is true. So either moral absolutism is true, or moral relativism is true. They cannot both be true. So if it is possible to show that moral relativism is not true then we are left with moral absolutism. This is what I will do here. My argument looks like this:
Premise 1: Either moral absolutism is true, or moral relativism is true.
Premise 2: Moral relativism is not true.
Conclusion: Therefore moral absolutism is true.
I will present a few points–which might overlap each other–as to why moral relativism is not true, and why moral absolutism, as the only alternative, has to be accepted instead.
The Moral Relativist Contradicts Himself
Moral relativism is the idea that no absolute moral standard exists, and that morality is relative to time, place and circumstances. Moral relativism leads to the conclusion that no absolute moral standard exists, because if moral relativism is true, then reality dictates that all alleged moral virtues are subjective opinions only, and that no one is morally obliged to follow any of them. On moral relativism all actions are morally equal, so to defend moral relativism while, at the same time, hold a certain normative moral position is self-contradictory. The moral relativist commits precisely this fallacy, since he, while defending moral relativism, adheres to quite a few moral virtues such as honesty, trustworthiness, integrity, honoring the rules of logic, arguing without bias, not lying, etc. In addition the atheist usually also adheres to moral virtues such as mutual respect (at least a certain degree), and the absence of the use of physical force. Some moral relativists go even further in expressing moral views while denying moral absolutism, e.g. “We all ought to be moral relativists”, “Moral absolutism is morally inferior to moral relativism”, “absolute morality is evil”, etc.
Imagine that the atheist wanted to conduct a debate while admitting that he did not care about any of the above mentioned moral virtues. In other words, if he thought that lying, being illogical, and using all kinds of rhetorical trickery was acceptable. It would not make any sense. In order to advance his argument the atheist must adhere to moral virtues, and this is precisely what he does.
So, all moral relativists necessarily hold moral positions while defending their arguments for moral relativism, and this makes them contradict reality as reality would look like if moral relativism were true. The moral relativist’s moral philosophy will dictate things like “You ought to do X” and “You ought to refrain from doing Y” while the objective reality on moral relativism would dictate “There is nothing you ought to do”.
In other words, if moral relativism is true and we want to live a philosophically consistent life we have to hold no normative moral position at all. But this is impossible for the moral relativist, making his position self-defeating.
The Moral Relativist Cannot be Trusted
From the above it follows that the moral relativist, in his adherence to moral relativism, has no reason to hold himself accountable to any moral obligation. But if he does not he cannot even trust himself, since there is no moral obligation to not be self-deceiving. Neither can we trust him. Thus his defence of moral relativism becomes absurd. Since any person arguing for moral relativism cannot be trusted, not even by himself, it also follows that his arguments for moral relativism cannot be trusted.
The True Moral Relativist Would be a Monster
Further, if a moral relativist really tried to live according to moral relativism, i.e. to live as if every action is morally equal to every other action, this would make him a morally crippled monster. At least in the eyes of the average person. He would, for example, not try to further or praise good deeds, and stop or condemn bad deeds. He would be justified in engaging in all kinds of morally objectionable actions.
The Moral Relativist Has Innate Knowledge of Moral Virtues
What we have learned from the above is that moral relativism is a self-contradiction. We all know that not all moral actions are equal. The truth is that we all have access to God-given innate knowledge of the fact that some things are really morally right, and some things are really morally wrong. This is evidenced by the impossibility of holding the moral relativistic point of view without self-contradiction, and by the unavoidable presence of moral virtues even in the staunchest adherent of moral relativism. The Christian philosopher and theologian Dr. William Lane Craig writes:
“…could anything be more obvious than that objective moral values do exist? There is no more reason to deny the objective reality of moral values than the objective reality of the physical world.” […] “The fact is that we do apprehend objective values, and we all know it. Actions like rape, torture, child abuse, and brutality are not just socially unacceptable behavior–they are moral abominations.” […] “By the same token, love, generosity, equality, and self-sacrifice are really good. People who fail to see this are just morally handicapped, and there is no reason to allow their impaired vision to call into question what we see clearly.” 
Since we all, at least deep within ourselves, know that something is really right, and that something is really wrong it becomes impossible to be a true moral relativist. This is seen by the fact that everyone is assuming moral absolutism in their every day affairs, and it becomes even more obvious when they are confronted with questions like “Do you really think it is true that pedophilia is not morally wrong?” or “Do you really think it is true that it is not wrong to torture babies for fun?” To press them with questions like this will force them to choose between accepting an absolute and objective morality, or be a self-contradictory, irrational, morally crippled monster. No matter what they choose theism is defended.
The moral relativistic position is invalidated as a coherent philosophical position in the sense that as soon as the moral relativist starts to defend moral relativism he affirms moral absolutism. Moral absolutism is therefore unavoidable, and must be accepted.
The above points makes it clear that the price one has to pay for adopting moral relativism is very high. One can only cling to moral relativism if one is willing to 1) think inconsistently 2) act inconsistently 3) contradict reality and 4) be a morally crippled monster. None of the above problems follows necessarily from moral absolutism, and since moral absolutism is the only possible alternative to moral relativism, we have to accept moral absolutism. And since God is the only foundation for absolute moral values we also have to accept the existence of God.
 “The Indispensability of Theological Meta-ethical Foundations for Morality” by Dr. William Lane Craig (http://www.leaderu.com/offices/billcraig/docs/meta-eth.html)